Conventionally, the fundamental concept of a filling method of powder, such as toner powder for electro photography, is that the powder from a large-sized container is dropped by its gravity into a small toner container arranged right under the large-sized container, and the small toner container is filled up with the powder. In this method, there are a rotary valve type, a screw feeder type, and an auger machine type. Especially the auger machine type method is known as the method which fills up the container of a fixed volume with the powder efficiently, and it is put in practical use. For example, see Japanese Laid-Open Patent Application No. 04-087901 and Japanese Laid-Open Patent Application No. 06-263101.
Immediately after the toner is filled into the small toner container by such powder filling method, a lot of air is contained between the powder particles. In order to store a lot of powder in a high-density state in the container for a short time, a suction pipe is inserted into the container so that the leading edge of the suction pipe is buried in the powder within the container, so that deaerating is performed with the suction pipe. For example, see Japanese Laid-Open Patent Application No. 09-193902.
Usually, in the auger machine type method, the auger machine in the shape of a screw provided in the inside near the outlet of a conic hopper is rotated, and the toner powder in the hopper is discharged downwardly from the outlet. And, after the discharging, the toner powder is stored in two or more containers arranged and conveyed on the transportation belt one by one.
In recent years, as for the image formation by the electrophotographic printing method, there is the increasing demand for improvement in the speed, highly-minute image, high image quality etc. With this demand, there are also various studies for developing toner powder, in order for micrifying the grain size of toner powder, sticking a metal oxide particle (called an external additive) to the surface of toner powder to increase the flowability, or securing low-temperature fixability using a binder resin with a low fusing point. Such studies are put into the practical use.
However, the toner powder will be pressurized by rotation of the auger machine according to the above-mentioned auger machine type method, and there is a problem in that the external additive may be separated or isolated from the surface of toner powder, and may be further buried into the toner powder. And the problem arises in that the original function of the external additive to increase the flowability is reduced or eliminated.
In addition, in a case of a low-temperature fixing toner powder with which a binder resin with a low melting point is used, the toner powder adheres by the pressurization by rotation of the auger machine, and it becomes easy to create the cohesion. It sometimes solidifies so that the cohesion does not return to the toner powder. As a result, the toner powder will be got blocked with the exit of the hopper, the discharging will stop, and the problem of interfering with the filling work of the toner also arises.
Originally, the more easily the toner powder falls to the container from the hopper, the more the grain size becomes smaller. And the Brownian motion is easily performed in a gas regardless of the kind of the source material and the toner powder is easily set in an atomizing state. As a result, the necessity of discharging a lot of gas existing between the powder particles will arise, and it will be difficult to form the high-density filling state of the toner powder in the container. Thus, it is desired that the above-mentioned problem will be solved with respect to such difficulty.
Moreover, as mentioned above, the auger machine serves as a large-scale device which requires at least the hopper and the filling machine including the belt on which two or more small toner containers are carried and conveyed, and the container concerned must be arranged at the location just under the filling machine. There is the problem in that the arrangement of the auger machine must be a fixed one and has some restrictions.
Furthermore, the toner powder for electrostatic latent image development is of a very small diameter, and the specific gravity is smaller than other powders, such as that of a ceramic material, but the flowability is poor and the coherence is high.
Recently, in order to reply to the demands for higher resolution of the developed image, the use of the toner powder for electrostatic latent image development of a smaller diameter is progressing increasingly. In addition, it is in the tendency that a resin with a low-temperature fusibility is adopted increasingly in order to reply to the demand of energy saving and instant high-speed fixing. The coherence, and the adhesion to other object surface and the filming nature are the other problems, and improving these features or avoiding the fluidity fall and the condensation is desired.
In many cases, for that purpose, it is used in the form where the toner particle surface is contained with the ultrafine particles, such as a flow improver and a condensation inhibitor, and contained with the charge modifier ultrafine particles for improving the charging characteristics. The agitation and the transfer by the auger machine or the screw conveyor which give superfluous stress to the toner are not desirable from a viewpoint of preventing the separation or isolation of the ultrafine particles with which the toner surface is supported, and ensuring the charging characteristics, the flowability, and the condensation-proof characteristics.
Especially, in the case of a color toner, the toner has a small grain size in order to acquire high resolution, and the components, such as a flow improver, an electrification modifier, a plasticizer, a condensation inhibitor, and a fusion inhibitor, are supported on the toner surface. The grains become entangled, and the flowability is poor. Moreover, when a strong external force is added, there is a danger of spoiling the characteristics of the toner, and the conventional mechanical treatment devices, such as the rotary valve type or the auger machine type, are not preferred.
Moreover, when air is mixed with the toner for the pneumatic treatment of the toner, the toner clouds (the toner particles in the form of cloud which is formed by mixing the toner with a gas) are created due to the floating of the superfine toner particles, and the volume which should be dealt with is increased.
In order to promptly separate the gas from the toner cloud and to make handling easy, it is difficult to attain the prompt separation only by consideration of the structure, the shape or the position of the separation piping. Therefore, it is difficult to control the amount of compression of the toner according to the separation of the gas for the transfer using the separation piping.
When a very fine toner is dealt with, if there is a too large amount of the supply air, a fluid phase will be expanded quickly and will shift to a dust phase easily. A long time may be taken to collect the toner from the once generated dust phase, or the circumference may be polluted with dust.
For example, once the toner clouds form, the standing of several hours or several tens of hours will be required only for making the toner deposit on the bottom by a natural fall. The operation for making the deposited toner fluidize and making it move to the small container for the subdivision, while the loose supply air is controlled, is not easy in order to control generation of a large amount of the toner clouds.
If the toner powder from a large-sized container is separated for many subdivision containers, the toner which is mixed to homogeneity initially may become the non-uniform components gradually under the influence of the air supplied into the container, and the necessity to take the countermeasure is proposed.
According to this proposal, the small containers are not filled with a toner powder directly from the large-sized container by the agitation and falling as in the auger machine type, but the toner from the large-sized container is delivered to a measuring tank temporarily, and the small toner container is filled up with the toner by using the measuring tank. This proposed method is to use a filling amount control unit for discharging only a given amount of the toner, among the toner delivered to the measuring tank, into the small toner container which is provided in the discharge opening of the measuring tank for the toner discharge.
Next, the new filling method according this proposal will be explained using the cross-sectional view of FIG. 1. FIG. 1 shows an example of the toner filling device used for the new filling method.
In the toner filling device of FIG. 1, a small toner container (40) is filled up with the very fine toner in a large-sized container (10) by using a measuring tank (30). The large-sized container (10) and the measuring tank (30) communicate with each other through the connecting tube (20) between the toner outlet (11) of the large-sized container (10) and the toner entrance of the measuring tank (30).
The measuring tank (30) has a filling amount control unit (32) at the discharge opening (31) where the toner is discharged into the small toner container, and the filling amount control unit (32) is provided for opening and closing the discharge opening (31) to fill up the small toner container (40) only with a given amount of the toner.
The large-sized container (10) has the inside wall portion (12) which is inclined in such a manner that it does not bar slipping down of the toner stored inside. And, by this inclined inside wall portion (12) inside, discharging of the very fine toner to the toner outlet (11) is carried out smoothly.
In the toner filling device of this example, the inclined inside wall portion (12) forms a part of the structural portion (13) of the lower portion of the large-sized container (10) in the shape of a hopper.
The large-sized container (10) and the measuring tank (30) are also connected with a top communicating pipe (50) formed in the upper part of the connecting tube (20), and this top communicating pipe (50) is inclined upward toward the large-sized container (10) from the measuring tank (30).
The top communicating pipe (50) serves to keep the pressure in the measuring tank (30) equal to the pressure in the large-sized container (10). And when a too large quantity of the gas is discharged from the 3rd toner fluidization unit (33) and too large toner clouds are formed in the measuring tank (30), the excessive amount of the gas can be extracted into the large-sized container (10) by using the top communicating pipe (50), and with the upward inclination of the top communicating pipe the toner grains accompanied therewith can be returned to the measuring tank (30).
The toner powder discharged from the toner outlet (11) of the large-sized container (10) bottom is delivered to the measuring tank (30) through the connecting tube (20).
In the measuring tank (30) in this example, the filling amount control unit (32) is provided in the discharge opening (31) for exact and smooth filling of the toner in only the given amount.
The filling amount control unit (32) in the powder filling device of this example comprises an elastic body ring (32a) having a discharge opening (31), and a discharge control unit (32b) which controls the discharge of the toner from the discharge opening (31). The discharge control unit (32b) comprises a discharge control member (32d) disposed in the discharge control lever (32c) which is moved up and down inside the measuring tank (30). The discharge control member (32d) is a member in the conical shape which intercalates—breaks away with a discharge opening (31), and which opens and closes the discharge opening (31) through the insertion into the discharge opening (31) and the separation from the discharge opening (31). The degree of the insertion into the discharge opening (31) is adjusted by the insertion degree and the fitting degree of the elastic body ring (32a) of the discharge control member (32d) of the conical shape which varies depending on the degree of the up/down movement of the discharge control lever (32c) within the measuring tank (30).
When the discharge control member (32d) is moved up so that the edge of the conical part of the discharge control member (32d) with the small radius is completely separated from the discharge opening (31), it is in the fully open state (the toner is freely discharged to fill the small toner container). When the discharge control member (32d) is moved down so that the based end of the conical part of the discharge control member (32d) with the large radius is completely fitted into the discharge opening (31), it is in the fully closed state (the discharging of the toner is stopped).
When the discharge control member (32d) is in the intermediate state (i.e., when it is not separated from the discharge opening (31) completely and is not descended completely, and it is not inserted in such a manner that a gap is held between the middle radius part of the discharge control member (32d) and the discharge opening (31)), it is in a half-opening state (partial discharging of the toner) according to the degree of the insertion.
As mentioned above, the new powder filling method proposed by the present inventor is characterized in that the powder in the large-sized container is delivered to the measuring tank temporarily, the powder filling container is filled up with the powder from the measuring tank directly, and the filling amount control unit for discharging the powder of only the given amount to the discharge opening of the measuring tank is provided.
In carrying out the new powder filling method concretely, the present inventor confirmed that the following new problems arise.    1. Filling of the powder and the air displacement in the container cannot be performed, and the powder may overflow.    2. the ratio of the amount of the powder and the quantity of the gas varies, and the flow rate may become unstable.    3. Because of the necessity for the gas discharge in the powder filling container, the powder discharge port of the measuring tank and the opening of the powder filling container cannot be sealed, and the powder may leak from a gap and disperse so that the powder filling device neighborhood is polluted with such powder.
Accordingly, an object of the present invention is to provide a powder filling device and method which is capable of making stable powder flow rate, preventing the powder from being leaked or dispersed during the filling operation, and filling the powder in a short time in carrying out the new powder filling method.